VASCULAR DISEASES -Continued. 



COBB'S DISEASE OF SUGAR-CANE. 



Synonyms: Gumming of Cane, Sereh in part (?), Top- rot in part (?), Polvillo (?). 



DEFINITION. 



This is a specific communicable disease of sugar-cane, due to a yellow, one-flagellate 

 schizomycete. The most conspicuous signs are dwarfing, etiolation, stripes on the leaves, 

 reduction of sugar-content, decay of the terminal bud, and the appearance in the fibro- 

 vascular bundles of a yellow slime and a red stain. In early stages of the disease this slime 

 is inconspicuous, but in later stages it is one of the most striking features of the disease 

 (see plate 11, fig. 2), and frequently gives trouble in the sugar- factory, gumming the ma- 

 chinery, interfering with the clarification, and delaying the boiling in the vacuum-pans. 



HOST PLANTS. 



So far as known, the disease is confined to the sugar-cane (Saccharum officinarum). 



GEOGRAPHICAL DISTRIBUTION. 



This disease occurs in New South Wales (Cobb, Greig Smith), Queensland (Tryon, 

 Cobb), Fiji Islands (Clark), Mauritius (Boname), Java (Went), Borneo (Kriiger), New 

 Guinea (Cobb), and Brazil (Dranert). From various statements in Spegazzini's paper on 

 Polvillo or humid gangrene of the cane I believe this disease is also present in Argentina, 

 Tucuman province (see Polvillo, p. 85). It is probably not in North America. No com- 

 plaints have been received from the cane-fields of Louisiana. Dr. Went did not find it, or 

 hear of it, in his tour of inspection in the Dutch West Indies in 1902. It has not been 

 reported from the British West Indies nor from Porto Rico. The writer did not see it, or 

 hear of it, in Cuba in 1904, nor was it seen in 1907 by John R. Johnston, assistant in the 

 Laboratory of Plant Pathology, who spent six months in the West Indies, visiting Cuba, 

 Jamaica, Trinidad, Guiana, Venezuela, Barbados, and Porto Rico, and who was instructed 

 to look for it especially. Recently a top-rot of sugar-cane has been reported from Cuba 

 by Cook and Home, but their account of it leaves very much to be desired. It does not 

 occur in the Sandwich Islands (Cobb). Sereh and cane-gummosis are said by Dr. E. J. 

 Butler to be "unknown or rare" in India (letter to our Secretary of Agriculture, April 21, 

 1903). It is a disease most prevalent in the Southern Hemisphere, but one likely to occur 

 wherever cane is grown. The Javan top-rot as described and figured by Wakker is not 

 this disease. Possibly, however, it may have been confused with the Javan heart-rot or 

 with the pokka-bong. 



HISTORY. 



Dranert was probably the first person to describe this disease in a scientific publication, 

 and certainly the first one to find bacteria in connection with it. His observations were 

 made more than 40 years ago in the great sugar region of the province of Bahia, in Brazil 

 (S. lat. 13). This disease had been present at the time of this first paper (1869) to a very 

 alarming extent for about 6 years, and recognized as a distinct disease for a much longer 

 period. During the "past three years," in the comarca of Nazareth, near the city of Bahia, 



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